"Indra's net" is the net of the VedicdevaIndra, whose net hangs over his palace on Mount Meru, the axis mundi of Buddhist and Hindu cosmology. In this metaphor, Indra's net has a multifaceted jewel at each vertex, and each jewel is reflected in all of the other jewels.[4]

Far away in the heavenly abode of the great god Indra, there is a wonderful net which has been hung by some cunning artificer in such a manner that it stretches out infinitely in all directions. In accordance with the extravagant tastes of deities, the artificer has hung a single glittering jewel in each "eye" of the net, and since the net itself is infinite in dimension, the jewels are infinite in number. There hang the jewels, glittering "like" stars in the first magnitude, a wonderful sight to behold. If we now arbitrarily select one of these jewels for inspection and look closely at it, we will discover that in its polished surface there are reflected all the other jewels in the net, infinite in number. Not only that, but each of the jewels reflected in this one jewel is also reflecting all the other jewels, so that there is an infinite reflecting process occurring.[5]

Book 30 of the sutra is named "The Incalculable" because it focuses on the idea of the infinitude of the universe and as Cleary notes, concludes that "the cosmos is unutterably infinite, and hence so is the total scope and detail of knowledge and activity of enlightenment."[7] In another part of the sutra, the Buddhas' knowledge of all phenomena is referred to by this metaphor:

They [Buddhas] know all phenomena come from interdependent origination.

The metaphor of Indra's net of jewels plays an essential role in the Chinese Huayan school,[9] where it is used to describe the interpenetration (Wylie: zung-'jug; Sanskrit: yuganaddha) of microcosmos and macrocosmos.[10] The Huayan text entitled "Calming and Contemplation in the Five Teachings of Huayan" (Huayan wujiao zhiguan 華嚴五教止觀, T1867) attributed to the first Huayan patriarch Dushun (557–640) gives an extended overview of this concept:

The manner in which all dharmas interpenetrate is like an imperial net of
celestial jewels extending in all directions infinitely, without limit. … As for the imperial net of heavenly jewels, it is known as Indra’s Net, a net which is made entirely of jewels. Because of the clarity of the jewels, they are all reflected in and enter into each other, ad infinitum. Within each jewel, simultaneously, is reflected the whole net. Ultimately, nothing comes or goes. If we now turn to the southwest, we can pick one particular jewel and
examine it closely. This individual jewel can immediately reflect the image
of every other jewel.

As is the case with this jewel, this is furthermore the case with all the rest of the jewels–each and every jewel simultaneously and immediately reflects each and every other jewel, ad infinitum. The image of each of these limitless jewels is within one jewel, appearing brilliantly. None of the other jewels interfere with this. When one sits within one jewel, one is simultaneously sitting in all the infinite jewels in all ten directions. How is this so? Because within each jewel are present all jewels. If all jewels are present within each jewel, it is also the case that if you sit in one jewel you sit in all jewels at the same time. The inverse is also understood in the same way. Just as one goes into one jewel and thus enters every other jewel while never leaving this one jewel, so too one enters any jewel while never leaving this particular jewel.[11]

The Huayan Patriarch Fazang (643–712) used the golden statue of a lion to demonstrate the Huayan vision of interpenetration to empress Wu:[12]

In each of the lion's eyes, in its ears, limbs, and so forth, down to each and every single hair, there is a golden lion. All the lions embraced by each and every hair simultaneously and instantaneously enter into one single hair. Thus, in each and every hair there are an infinite number of lions... The progression is infinite, like the jewels of Celestial Lord Indra's Net: a realm-embracing-realm ad infinitum is thus established, and is called the realm of Indra's Net.[12]

According to Rajiv Malhotra, the earliest reference to a net belonging to Indra is in the Atharva Veda (c. 1000 BCE).[13] Verse 8.8.6. says:

Vast indeed is the tactical net of great Indra, mighty of action and tempestuous of great speed. By that net, O Indra, pounce upon all the enemies so that none of the enemies may escape the arrest and punishment.[14]

And verse 8.8.8. says:

This great world is the power net of mighty Indra, greater than the great. By that Indra-net of boundless reach, I hold all those enemies with the dark cover of vision, mind and senses.[15]

The net was one of the weapons of the sky-god Indra, used to snare and entangle enemies.[16] The net also signifies magic or illusion.[17] According to Teun Goudriaan, Indra is conceived in the Rg Veda as a great magician, tricking his enemies with their own weapons, thereby continuing human life and prosperity on earth.[18] Indra became associated with earthly magic, as reflected in the term indrajalam, "Indra's Net", the name given to the occult practices magicians.[18] According to Goudriaan, the term indrajalam seems to originate in verse 8.8.8 from the Atharva Veda, of which Goudriaan gives a different translation:[19]

This world was the net of the great Sakra (Indra), of mighty size; by means of this net of Indra I envelop all those people with darkness.[19]

According to Goudriaan, the speaker pretends to use a weapon of cosmical size.[19] The net being referred to here

...was characterized there as the antariksa-, the intermediate space between heaven and earth, while the directions of the sky were the net's sticks (dandah) by means of which it was fastened to the earth. With this net Indra conquered all his enemies.[19]

"Imagine a multidimensional spider's web in the early morning covered with dew drops. And every dew drop contains the reflection of all the other dew drops. And, in each reflected dew drop, the reflections of all the other dew drops in that reflection. And so ad infinitum. That is the Buddhist conception of the universe in an image." –Alan Watts[20]

Buddhism uses a similar image to describe the interconnectedness of all phenomena. It is called Indra's Net. When Indra fashioned the world, he made it as a web, and at every knot in the web is tied a pearl. Everything that exists, or has ever existed, every idea that can be thought about, every datum that is true—every dharma, in the language of Indian philosophy—is a pearl in Indra's net. Not only is every pearl tied to every other pearl by virtue of the web on which they hang, but on the surface of every pearl is reflected every other jewel on the net. Everything that exists in Indra's web implies all else that exists.[22]

Writing in The Spectator, Sarah Burton explains that Brook uses the metaphor, and its interconnectedness,

to help understand the multiplicity of causes and effects producing the way we are and the way we were [...] In the same way, the journeys through Brook's picture-portals intersect with each other, at the same time shedding light on each other.[23]

the profound cosmology and outlook that permeates Hinduism. Indra's Net symbolizes the universe as a web of connections and interdependences [...] I seek to revive it as the foundation for Vedic cosmology and show how it went on to become the central principle of Buddhism, and from there spread into mainstream Western discourse across several disciplines.[24]